U.S. President Barack Obama has emphasized to Russian President Vladimir Putin the importance of Moscow playing a constructive role by ceasing its air campaign against moderate opposition forces in Syria.

The White House said that Obama made the point in a phone conversation with the Russian president on February 14.

Obama also spoke of the need for getting humanitarian aid to populations besieged by fighting in the country.

The phone conversation came after world powers agreed in Munich on February 12 to work for a humanitarian truce in Syria to begin in a week's time.

The Kremlin said that Putin stressed to Obama the need to create a united international front against global terrorism.

Putin reportedly said that closer contacts were needed between U.S. and Russian military officials in order to successfully counter Islamic State and other terrorist groups.

Putin also expressed the hope that authorities in Ukraine will "promptly fulfill their obligations" under the Minsk process to regulate the conflict in eastern Ukraine between Kyiv and Russia-backed separatist militants, according to the statement.

Western countries have blamed Russian air strikes in Syria and support for the government of President Bashar al-Assad for the worsening security situation there.

And on February 13, U.S. Secretary of State John Kerry said Moscow had failed to implement its obligations under the Minsk process, including the withdrawal of Russian forces from Ukraine and handing over to Kyiv complete control over Ukraine's borders.